1. Field of the Invention
The present invention relates to an imaging apparatus that is used for obtaining three-dimensional (3D) information on a subject, and a method of controlling displaying images on the imaging apparatus. The present invention also relates to a 3D information obtaining system that includes the imaging apparatus.
2. Description of the Related Art
A pantoscopic camera captures more than one image of a subject at a time from different viewpoints, and these images may be used for obtaining 3D information about the subject, which represents the spatial position of the subject in a predetermined spatial or 3D coordinate system. The 3D information may be obtained using a known distance calculation method, such as disclosed in JPA 1993-231822, wherein correspondence of pixels between a pair of images captured at the same time is determined using one of various matching methods. On the basis of respective pairs of corresponding pixels and stereo-calibration data, such as a reference length of the pantoscopic camera, distances from the pantoscopic camera to multiple points on the subject that correspond to the respective corresponding pixels are calculated to be 3D coordinate values.
The above-mentioned distance calculation can provide 3D information of only those pixels which are within overlap areas of each pair of images. In order to obtain 3D information from a particular subject, the user should frame the scene so as to contain the particular subject within the overlap area before pressing the shutter button, or in a camera as disclosed in JPA 1999-88811, before an automatic image-capturing starts.
Generally, framing is done while watching the subject through a viewfinder or a through-image displayed on a monitor that functions as an electronic viewfinder. In one pantoscopic imaging apparatus disclosed in European Patent No. 0 645 926 B (corresponding to JPA 1995-95467), a composite image is produced by combining a pair of images on the basis of detected overlap areas of these images, and the composite image is displayed on a monitor as a through-image. In a stereo camera disclosed in JPA 2006-121229, overlap areas are detected from a pair of images of an identical scene or subject, and a framing window or border line of the overlap area is overlaid on a through-image corresponding to the pair of images.
U.S. Pat. No. 6,809,771 (corresponding to JPA 2001-12910) discloses a multi-scope data input apparatus that crops a subject image area containing an aimed subject from each of a pair of captured images, to display an image having the subject image areas overlaid on one another. On the basis of this prior art, it may be possible to crop an overlap area from each of a pair of images and display an image corresponding the overlap areas.
According to the methods disclosed in European Patent No. 0 645 926 B (corresponding to JPA 1995-95467) and JPA 2006-121229, the composite image displayed as a through-image contains not only the overlap area but also non-overlap areas of the respective image pair. Therefore, when deciding the framing position, the user cannot exactly check if the aimed subject is contained in the overlap area. According to the method disclosed in U.S. Pat. No. 6,809,771 (corresponding to JPA 2001-12910), on the contrary, the through-image merely contains the overlap area even before the user does not decide on the framing, and the user cannot check the wider range of the view field of the camera. This is inconvenient for the user to decide on the framing.